Refrigeration



` Sept. 2, 1941. w. H. KITTo 2,254,658

REFRIGERATIDN Filedvoct. 1o, 195s INVENTOR ATTORNEY Patented Sept. 2, 1941 REFnIGEnAnoN William H. Kitto, Canton, Hoover Company, North ration of Ohio Ohio, assignor to The Canton, Ohio, a corpo- Application October 10, 1938, Serial No. 234,110

9 Claims.

4with a velocity high enough to drag or sweep the liquid refrigerant along therewith; the height of the evaporator may be so great that the gas circulating through the evaporator-absorber system is not placed under sufficient pressure to lift the liquid refrigerant entirely through the evaporator; the inert gas may be too light to elevate the liquid through the fully height of the evaporator; and with some systems it may be desirable to extend the evaporator below the condenser and to connect the two by a short direct connection.

There is disclosed in the copending application i Serial No. 220,188, filed July 20, 1938, o f Curtis C.

Coons and William H. Kitto a refrigerating system including an evaporator of the general type herein disclosed; however, in the said prior applicatior. a very complex draining system is required to perform the dual function of draining the liquid refrigerant from the gas outlet portions of the evaporator into the gas inlet portions thereof while insuring that the drain will automatically seal itself to prevent inert gas from by-passing through the drainage system very shortly after the evaporator goes into operation. This evaporator operates satisfactorily but it does not quickly reach normal operating condition because the drain from the gas outlet to the gas inlet portions of the evaporator acts as an inert gas by-pass until liquid refrigerant can counterflow through a portion of the evaporator in sufficient quantities to ll a complex drainage and gas sealing system.

Accordingly, it is a principalobject of the instant invention to provide an evaporator of the general type disclosed in the said copending application in which the draining system is always prevented from acting as a gas by-pass and which further insures that liquid refrigerant will properly drain from the gas outlet portions of the evaporator to the gas inlet portionsthereof.

It is a further object of this invention to provide a refrigerating system including an evaporator of the above referred to type which will prevent gas from by-passing .through the liquid wardly through the (Cl. G15-119.5)

refrigerant drain connecting the gas inlet and outlet portions of the evaporator.

It is a further object of the present invention to provide an evaporator of the type having a liquid drain between the gas inlet and outlet portions thereof with a drain construction which will insure initial starting of the apparatus and will thereafter continuously maintain a body of liquid in the drain suicient to prevent gas from by-passing therethrough and to insure prompt re-starting of the apparatus in response to appropriate temperature conditions.

Other objects and advantages of the invention will become apparent as the' description proceeds when taken in connection with the accompanying drawing, in which:

Fig. l is a diagrammaticv representation of a three -uid absorption refrigerating system having the evaporator thereof illustrated in perspective and on an enlarged scale.

Figure 2 is a fragmentary partial sectional view of a detail.

The invention is illustrated as being applied to a continuous three-fluid absorption refrigerating system comprising a boiler B, an analyzer D, a rectifier R, a tubular air-cooled condenser C, an evaporator E, a gas heat exchanger H, 'a liquid heat exchanger-L, asolution reservoir S, a tubular air-cooled absorber A, and a circulating fan F which is driven by -an electrical motor M. These elements are suitably interconnected by various conduits to constitute a complete refrigerating system including 'a plurality of gas and liquid circuits to which reference will be made in more detail hereinafter.

The above described refrigerating system will be suitably charged with a refrigerant, such as ammonia, an absorbent, such as water, and a pressure equalizing medium, preferably a dense inert gas, such as nitrogen.

The boiler Bvwill be heated in any suitable manner as by a gas burner or an electrical cartridge heater. The boiler, heater and the circulating motor M may be controlled in any suitable or desired manne A preferred control mechanism is disclosed in the copending application of Curtis C. Coons, filed June 17, 1937, Serial No. 148,424.

of refrigerant and absorbent-contained in the boiler B passes upanalyzer D in counterow to strong liquor supplied thereto from a source to be described hereinafter whereby the refrigerant vapor is substantiallyfreed of vapor of absorption liquid. Refrigerant vapor is conveyed from the analyzer D to the condenser C by way of a conduit I|. An air-cooled rectifier R, which is included in the conduit Il, causes condensation of any vapor of absorption solution which may pass through the'analyzerl D. The refrigerant vapor is liquefied in the condenser C, which extends well below the top portion of the evaporator, preferably by heat exchange with the surrounding air, and is discharged therefrom4 through a. conduit |2leading to the evaporator.

The weak solution formed in the boiler B by the generation of refrigerant vapor is conveyed therefrom to the upper end of the absorber A through the conduit I5, the inner path of the liquid heat exchanger L, and a conduit |6. It is apparent that the upper end of the absorber is at an Velevation appreciably higher than the liquid level normally prevailing in the boiler-analyzer wherefore some means must be provided in order to elevate the weak solution into the absorber. For this purpose a small bleed conduit I1 is connected between the discharge conduit I8 of the circulating fan F and the weak solution conduit I6 below the liquid level normally prevailing therein whereby the weak solution is elevated into the absorber by gas lift action. The weak solution ilows downwardly through the absorber by gravity in counterflow with rich pressure equalizing medium flowing upwardly therethrough. The absorption solution and the pressure equalizing medium are brought into intimate contact. in the absorber whereby the refrigerant vapor content of the mixture is absorbed in the solution which thereby becomes strong solution. The heat of absorption is rejected from the absorber by means of cooling fins mounted on the exterior walls thereof to the surrounding air. The strong solution formed in the absorber flows to the low point of the rich mixture conduit 20 from which it is drained through a conduit 22 into the solution reservoir S. The solution collecting in the reservoir S is conveyed therefrom to the upper portion of the analyzer D by way of the conduit 23, the outer path of the liquid heat exchanger L, and a conduit 24.

The lean pressure equalizing medium formed in the absorber A is discharged therefrom through a 'conduit 28 into the suction inlet of the circulating fan F. The inert gas is placed under pressure by the fan and is discharged therefrom' through the conduit I8 into the outer path of the gas heat exchanger H. After passing through the outer path of the gas lean gas is conveyed therefrom to the bottom portion of the evaporator E through a conduit 30. The exact construction and operation of the evaporator will be described in detail hereinafter, for the present it is sufcient to note that the pressure equalizing medium flows upwardly through all portions of the evaporator in contact with the liquid refrigerant which evaporates into the inert gas to produce refrigeration. The rich mixture formed in the evaporator is discharged therefrom through .a conduit .3| into the inner path of the gas heat exchanger H. After passing through theinner path of the gas heat exchanger the rich mixture is conveyed therefrom -to the lower portion of the absorber A through the conduit 20.

Referring now to the evaporator in detail, it will be seen that it comprises a plurality of substantially horizontal 4parallel vertically spaced coil sections 35,.,36 and 31 and a superposed boxheat exchanger H, the.

half-way between the median planes cooling section 38 provided with a plurality of aircooling ns 39.`

Each of the coil sections 35, 36 and 31 comprises a spaced pair of U-shaped conduit elements 4| and 42 having the outer legs thereof connected Lby a conduit 43 extending across the rear portion of the evaporator. The inner legs of the U- shaped conduit sections form the inlet and outlet connections to each coil section. The gas inlet conduit 30 .opens into the inner leg of the conduit section 4|, andthe inner leg of the conduit lsection 42 is connectedto the corresponding leg of the coil section Similarly, the coil section 36 is'connected to the coil Vsectiton 31 by a riser conduit 45.. The coil section 31 is identical with the coil sections 35 and 36 except in that there is no member correspond' ing to the inner leg of the conduit sections 42 of the coil sections 35 and 36. In the coil section 31 the conduit section 42 is replaced by an L-shaped conduit 41 which terminates in a riser 48 opening into the front end of the box-cooling conduit 38.

'I'he coil sections 35, 35 and 31 and their -associated risers 44, 45 and 48 may be constructed from a single continuous tube or from a plurality of appropriately formed welded tube elements as desired.

The box-cooling conduit 38 slopes slightly rearwardly, as viewed in Figure 1, in order that the liquid may flow therethrough by gravity. The rear end of the conduit 38 adjacent the point of connection to the rich mixture conduit 3| is provided with a depending well 50 which is in open communication vwith a drain conduit 5I. The drain conduit 5| extends below the plane of the coil section 35 and then turns upwardly to join the rear end of an extension 53 on the inner leg of the conduit section 4|. The conduit 5| extends into the extension 53 a slight distance above the bottom portion thereof. A bimetallic thermostatic element 55 is rigidly'mounted on the bottom wall of the extension 53 at 56 and the free end of the bimetallic `thermostat 55 extends across the open mouth portion of theconduit 5| in position to close the same.

The bimetallic thermostat 55 does not fully seal the drain conduit 5l; it is only necessary that it seal the same sufficiently to prevent any1 material gas `iow therethrough which would prevent liquid from flowing through the drain 5| from the box-cooling conduit and would also tend to lower the gas velocity in the coil sections 35 and 31 suiciently to prevent propulsion of the refrigerant by the inert gas.

The dead endedv extension 53 is l positioned slightly below the plane of the coll section 35 to which it is connected by an inclined conduit section 58. The lean gas conduit 30 opens into the inclined conduit 58 at a point approximately of the extension 53 and the coil section 35.

A drain conduit 60- cornmunicates the conduit section 42 adjacent its point of connection with the riser conduit 44 and the strong solution return line 23.

The above described evaporator is constructed and arranged in such fashion that it may be enclosed in any suitable form of casing to provide a plurality of shelvesupon which watercontaining ice cube freezing trays may conveniently be mounted.

Though the apparatus has been shown diagrammatlcally herein, it is to be understood that it may be incorporated iiiany desired form of cabinet.

36 by -a riser conduit 44..

The operation of the invention will now be described. Assuming that the apparatus has not been operating and that the evaporator is warm, the liquid refrigerant discharging from the condenser C through the conduit I2 will enter the cross connecting conduit 43 of the coil section 36. The high temperature of the evaporator will have causedthe thermostatic element 55 to flex downwardly, as viewed in Figure 2, to a position substantially sealing the inlet of the conduit 6|; therefore, it will not be possible for inert gas discharged through the conduit 30 to by-pass through the conduit into the outlet portion of the box-cooling coil to any material extent. If this short by-pass for the gas stream is blocked by .the thermostaticelement, all the inert gas discharged into the evaporator must ow through the relatively small diameter evaporator conduit.

This gas stream will therefore flow at a relatively`- high velocity and will sweep or drag the liquid refrigerant discharged into the conduit 43 through the coil section 36, the riser conduit 45, the coil section 31 and into the box-cooling coil 38. A full explanation of this phenomena will be found in the copending applications of Curtis C. Coons and William I-I. Kitto, Serial Nos. 220,188 and 220,189, filed July 20, 1938. The liquid flows through the relatively large diameter box-cooling conduit 38 by gravity as the relatively slowly moving inert gas stream is unable to propel .the liquid through that conduit.

Any liquid not evaporated in the conduit 3B falls into the well 50 from which it is drainedinto the conduit 5|. The liquid refrigerant collects in the conduit 5| until it has lled the lowest U- shaped portion thereof after which it leaks through the imperfect seal formed by the bimetallic.l thermostat '55 and the open-mouth portion of .the conduit 5| into the extension 53. This procedure continues until sufficient liquid refrigerant has collected in the extension 53 to bring the forward-end of the liquid pool into the gas propulsion zone just adjacent the points of connectionbetween the conduits 58 andv 30. Immediately this occurs, liquid refrigerant is brought will be stored in the lower portion thereof to form the balancing liquid column without breaking the seal.

The bi-metallic thermostat 55 does not cycle with the normal cycling control of the apparatus for the reason' that once the apparatus has been in normal operation there will be sufficient liquid refrigerant within .the conduit 5| when the apparatus discontinues operation to maintain the liquid seal therein and to form the pressure balancing column when the circulating fan is reenergized. The bi-metallic thermostat 55 is so calibrated that it will not move to closed position unless the temperature thereof shall have been raised to a value in the neighborhood of or 36 F. so there is no reason for closing the mouth of the conduit .5I during normal operation of the apparatus after the conduit 5| has become sealed with liquid. During normal cycling of the apparatus the control does not permit the temperature of the evaporator to reach a value above the freezing point of ice. Therefore, the thermostat 55 remains substantially inoperative.

'Ihe liquid refrigerant collecting in the extension 53 and the lower portion of the conduit 5| during the inactive period of the apparatus does not evaporate as there is no inert gas stream owing through the evaporator into which such evaporation could occur and because the control does not permit the temperature to rise suiciently to evaporate this liquid.

Therefore, it will be seen that the liquid refrigerant is supplied to the central portion of the evaporator through the conduit I2 from which it into contact with a moving body of inert gas and begins to evaporate producing a relatively low temperature in the region of the bi-metallic thermostat 55. Since the conduit 5| is now effectively sealed with liquid refrigerant, it is no longer necessary that the bi-metallic thermostat should partially block the open end of the conduit 5| As the production of refrigeration continues in the lower portion of the evaporator, .the temperature within the extension 53 is gradually lowered and the bi-metallic thermostat 55 flexes upwardly to the position indicated in dotted lines in Figure 2. Not all the liquid refrigerant discharging into the conduit 53 evaporates directly adjacent the points of connection between the conduits 30 and 58, but a suiiicient vquantity thereof is swept through the coil section 35 by the inert gas streaml to produce lrefrigeration in all portions of that coil section.

An appreciable pressure differential exists between the conduits 30 and 3l and the liquid refrigerant collecting in the'conduit 5I'must form a pressure balancing liquid column in the longer leg of that conduit suiiicient to overcome this pressure differential. 'Ihis occurs immediately the thermostat 55 opens sumciently from the conduit 5| to reduce throttling action thereupon to a negligible value. However, this does not break the liquid seal formed in the conduit 5I for the reason that sufcient liquid refrigerant '5| into the inlet 53 where it is swept by the inert gas stream through onehalf of the central portion of the evaporator, through the top coil sections thereof, and into the box-cooling section through which it flows by gravity. From the box-cooling section the liquid refrigerant is drained through the conduit is again brought into contact with the high velocity gas stream and propels the same into the lowest -coil section.

It is not definitely known whether the refrigeration is produced in the riser 44 and in the right hand portion of the coil 36 -by liquid refrigerant blown upwardly thereinto from the lowest coil section, by liquid refrigerant counterflowing to the inert gas stream, or by the very cold inert gas stream supplied from the lowest coil section. At all events, refrigeration is prpduced in all portions of the evaporator.

It is apparent that by-passing of the inert gas stream is always prevented by accumulated liquid remaining in the liquid seal portions of the conduit 5| after initial starting of the aparatus unless some abnormal condition has intervened to drive the liquid out of the sealing portion of the evaporator. If the evaporator should be funsea-led, the seal is restored by repeating the initial starting cycle.

'Ihere is another reason for sealing the conduit 5I which is that even if the inert gas stream velocity through the upper portions of the evaporator was suicient to sweep liquid refrigerant upwardly into the box-cooling coil, 'such liquid would not by-passdownwardly through the drain 5|, if the same were wide open, counter to the gas stream entering through the conduit 30 for the reason that the gas velocity through the conduit 5| would be suiciently great to blow all liquid refrigerant flowing to the inlet thereof in the box-cooling coil away from such inlet, and leventually would cause su'ch liquid to return to the lower portion of the absorption solution circuit through the gas heat exchanger.

While the invention has been illustrated and described herein in considerable detail, it is not to be construed as being limited thereto but other constructional forms and variations may be resorted to without departing from the spirit of the invention or the scope of the appended claims.

I claim: c

l 1. Refrigerating apparatus comprising an evaporator, means for propelling a dense inert gas through said evaporator, means for supplying refrigerant liquid to an intermediate portion of said evaporator, means for draining liquid refrigerant from the top portion of said evaporator to a lower portion thereof, and means substantially closing said drain means adapted to open the same in response to the accumulation of a predetermined quantity of liquid in said drain.

2. Refrigerating apparatus comprising an evaporator, means for propelling a .dense inert gas through said evaporator, means for supplying refrigerant liquid to an intermediate portion of said evaporator, means for draining liquid refrigerant from the top portion of said evaporator to a lower portion thereof, and a thermostatic valve closing said drain means against material gas ow adapted to open when cooled by evaporation of the liquid refrigerant flowing therethrough.

3. Refrigerating apparatus comprising an evaporator, means for propelling a dense inert gas through said evaporator, means for supplying refrigerant liquid to anintermediate portion of said evaporator, means for draining liquid refrigerant from the top portion of said evaporator to a lower portion thereof, a liquidtrap gas sealing device in said drain means, and a thermostatic valve substantially closing said drain means adapted to open when cooled by evaporation of the liquid refrigerant collected in said gas sealing device.

4. An evaporator structure comprising a plurality of serially connected coil sections positioned in vertically spaced horizontal planes, means for supplying liquid refrigerant to an intermediate one of said coil sections, means for draining liquid refrigerant elevated through said evaporator from the gas outlet thereof to the lowest section thereof, and thermostatic means for controlling fluid flow through said drain.

6. Refrigerating apparatus comprising a vertically extending evaporator, means for propelling a pressure equalizing medium upwardly through said evaporator, means for supplying liquid Iefrigerant to an intermediate portion of said evaporator, a dead e`nd extension on the gas inlet portion of said evaporator, a conduit including a gas sealing liquid trap communicating said extension and the gas outlet portion of said evaporator, and athermostatic valve for said conduit in said extension.

7. Refrigerating apparatus comprising an evaporator, means for propelling an inert gas through said evaporator under conditions such that it will sweep liquid therethrough, means for supplying liquid refrigerant to said evaporator, means for conveying unevaporated liquid from the gas outlet portion of the evaporator to the gas inlet portion thereof, a liquid seal portion included in said conveying means, and a thermostatic valve closing said conveying means except for a small leak port positioned to be actuated by refrigeration produced adjacent the gas inlet portion of said evaporator.

8. Refrigerating apparatus including an evaporator comprising a plurality of spaced freezing sections, a box-cooling section, means for supplying liquid refrigerant to one of said freezing sections, means for propelling inert gas through said sections with a lvelocity sufficient to sweep or drag refrigerant liquid therethrough and in a direction' to convey refrigerant liquid from said freezing sections into said box-cooling section,

means for conveying liquid refrigerant from said box-cooling section to another of said freezing sections, and means for substantially preventing direct flow of inert gas between said box-cooling section and said second mentioned freezing section.

9. Absorption refrigerating apparatus comprisdraining liquid from the outlet of the uppermost coil section to the inlet of the lowermost coil section, and means for substantially sealing said drain means against gas ow when liquid is not flowing therethrough.

5. Refrigerating apparatus comprising a boiler, a condenser, an absorber, an evaporator. means for conveying refrigerant vapor from said boiler to said condenser, means for supplying liquid refrigerant from said condenser to the central portion of said evaporator, means interconnecting said evaporator and said absorber to form a pressure equalizing medium circuit, means for propelling a pressure equalizing medium through said circuit, said circuit being arranged to supply pressure equalizing medium under pressure to said evaporator, means for ing a lsource of refrigerant vapor, a refrigerant liqueer connected to receive refrigerant vapor from said source, an evaporator extending to a level below said refrigerant liquefying means and connected to receive refrigerant liquid from said refrigerant liqueer at an intermediate level thereof, means for propelling inert gas upwardly through said evaporator with sufficient velocity and pressure to elevate refrigerant liquid from thel level at which refrigerant liquid is supplied to said evaporator to the upper portion thereof, meansfor conducting unevaporated liquid from the upper portion of said evaporator to the portion thereof which is positioned below said liquefying means, and means for substantially closing saidconducting means adapted to open the same when a predetermined quantity of liquid collects in said conducting means.

WILLIAM H. KITIO. 

